In a U-tube, as shown in the figure, the water and oil are in the left side and right side of the tube respectively. The height of the water and oil columns are $15\text{cm}$ and $20\text{cm}$ respectively. The density of the oil is (${\rho }_{water}=1000{\text{kg/m}}^3$):

1. A
   $1200{\text{kg/m}}^3$
2. B
   $750{\text{kg/m}}^3$
3. C
   $1000{\text{kg/m}}^3$
4. D
   $1333{\text{kg/m}}^3$